import javax.swing.tree.TreeNode;

/**
 * @author: 子龙
 */

public class BinarySearchTree {
    static class TreeNode{
        public int val;
        public TreeNode left;
        public TreeNode right;
        public TreeNode(int val){
            this.val = val;
        }
    }



    public TreeNode root;

    public void insert( int key){
        if(root == null){
            root = new TreeNode(key);
            return;
        }
        TreeNode parent = null;
        TreeNode current = root;
        TreeNode node = new TreeNode(key);

        while(current != null){

            if(current.val< key){
                parent = current;
                current = current.right;
            } else if(current.val > key){
                parent = current;
                current = current.left;
            }else {
                return;
            }

        }
        if(parent.val>key){
            parent.left = node;
        }else {
            parent.right = node;
        }
    }


    public TreeNode search( int key){
        if(root == null){
            return null;
        }
        TreeNode current = root;

        while(current != null){
            if(current.val<key){
                current = current.right;
            }else if(current.val== key){
                return current;
            }else {
                current = current.left;
            }

        }
        return null;
    }

     public void remove(int key) {
        TreeNode cur = root;
        TreeNode parent = null;
        while (cur != null) {
            if(cur.val < key) {
                parent = cur;
                cur = cur.right;
            }else if(cur.val > key) {
                parent = cur;
                cur = cur.left;
            }else {
                removeNode(parent,cur);
                return;
            }
        }
    }

    private void removeNode(TreeNode parent, TreeNode cur) {
        if(cur.left == null) {
            if(cur == root) {
                root = cur.right;
            }else if(parent.left == cur) {
                parent.left = cur.right;
            }else {
                parent.right = cur.right;
            }
        }else if(cur.right == null) {
            if(cur == root) {
                root = cur.left;
            }else if(parent.left == cur) {
                parent.left = cur.left;
            }else {
                parent.right = cur.left;
            }
        }else {
            TreeNode targetParent = cur;
            TreeNode target = cur.right;
            while (target.left != null) {
                targetParent = target;
                target = target.left;
            }
            cur.val = target.val;
            if(targetParent.left == target) {
                targetParent.left = target.right;
            }else {
                targetParent.right = target.right;
            }
        }
    }
}

